The invention relates to a device for trapping fuel vapors during the refuelling of a fuel tank, having a control valve located above the maximum fuel fill level of the tank to allow passage of fuel vapor from the tank to an activated carbon filter during refilling of the fuel tank and which denies passage of fuel vapors when the refilling ceases.
In a known device of this kind (German Offenlegungsschrift No. 3,605,708), a self-closing control valve is installed in the filler pipe of the fuel tank. When the filler pipe is closed, it ensures that there is no connection between the activated carbon filter and the fuel tank and that a desired positive pressure is thus maintained in the fuel tank. In addition, it also ensures that no fuel can escape into the open via the activated carbon filter in the event of the fuel tank being in an inclined or upside down position due to an accident.
For refuelling, this control valve is brought into its open throughflow position so that the fuel vapors, which are composed of hydrocarbons and are hence highly detrimental to health, cannot flow out of the fuel tank into the atmosphere but can flow off into the activated carbon filter.
In this arrangement, the filler nozzle of a fuel dispenser is introduced into the filler pipe and is used for opening the control valve. In order to avoid relatively large quantities of fuel vapors being able to flow out into the open end of the filler pipe even as the filler nozzle is being introduced, a guide channel restricts the filler pipe and has an inner end held closed by means of a self-closing closure flap provided for the filler nozzle inside the filler pipe. A forked operating lever associated with the value element of the control valve is secured on this closure flap. A tubular seal which surrounds the fuel dispenser filler nozzle at its outer periphery is provided inside the guide channel for sealing the nozzle upon its insertion into the pipe.
When the fuel dispenser filler nozzle swivels the closure flap into its open position, the fork legs of the operating lever come to rest against a head of a valve element shaft of the control valve and pull the valve element against the action of a restoring force into an open position, which establishes a connection of the fuel tank to the activated carbon filter. The fuel vapors can thus flow off during refuelling without escaping from the opened filler pipe.
A disadvantage in this construction is that it is necessary for the self-closing control valve to function perfectly in the event of the fuel tank being in an inclined or upside down position due to an accident, in order to insure that no fuel will flow from the fuel tank to the active carbon and thereby into the open atmosphere. However, such functioning is not guaranteed in the event of a crash when the filler pipe is deformed. For example, the control valve area or the valve element could be displaced in the direction of its open position in such a deforming happenstance. In addition, accommodating the control valve as well as guiding and sealing the fuel dispenser filler nozzle in the filler pipe is expensive in terms of construction and requires connections on the filler pipe for two fuel vapor lines which are to be installed outside the latter to be guided away from the fuel tank and which can easily be torn off in the even of an accident.
The object on which the instant invention is based is therefore to improve a device for trapping fuel vapors during the refuelling of a fuel tank, having a control valve located above the maximum fuel fill level of the tank to allow passage of fuel vapor from the tank to an activated carbon filter during refilling of the fuel tank and which denys passage of fuel vapors when the refilling ceases. The improvement provides: that even when the control valve does not close, or no longer closes perfectly, fuel cannot flow into the activated carbon filter in the event of the fuel tank being in an inclined or upside down position; that the control valve works independently of the introduction of the fuel dispenser into the filler pipe; that the control valve and tank can be located away from the filler pipe, in an accident-safe zone; and that only a single fuel vapor line, leading from the control valve to the activated carbon filter, has to be installed.
This object is achieved by having the control valve form a part of a valve unit which, comprises at least one further safety valve which is connected upstream of the control valve and which closes automatically under the influence of gravity from a certain inclined position of the fuel tank to interrupt the connection of the control valve with the interior of the fuel tank.
This valve unit can be installed at a suitable location on the upper wall part of the fuel tank so that it fits into the latter and that with the safety valve open, a direct connection between the tank interior and the control valve is ensured without an additional connecting line.
The equipping of the valve unit with just two valves is sufficient, provided that when the maximum fuel level is reached, the fuel has also risen in the filler pipe to such an extent that the automatic shut-off device of the fuel dispenser can come into operation and the supply of fuel into the tank is interrupted.
If, on the other hand, the orifice of the filler pipe is a long way above the maximum fuel level, it should include a float valve connected upstream of the safety valve to close off the vapor line when the maximum fuel tank level is reached and to thus allow fuel in the filler pipe to continue to rise after the closure of the float valve for the purpose of shutting off the fuel supplied by the fuel dispenser.
It is an advantage of the invention if a single valve unit house all the valves thus allowing for installation in an advantageous manner.
For the purpose of refuelling, it is advantageous if the control valve is power activated while the other valves are automatically actuated. The power control can be from a bowden cable attached to the filler pipe lid; a vacuum actuation from the engine; or an electric solenoid valve response to engine operation or vehicle movement.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.